drm/i915: Prevent stalling for a GTT read back from a read-only GPU target
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 590d8f2..7b37c19 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -729,6 +729,12 @@
unsigned int dirty : 1;
/**
+ * This is set if the object has been written to since the last
+ * GPU flush.
+ */
+ unsigned int pending_gpu_write : 1;
+
+ /**
* Fence register bits (if any) for this object. Will be set
* as needed when mapped into the GTT.
* Protected by dev->struct_mutex.
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index eae52de..c3e6d7b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1643,6 +1643,7 @@
obj->last_fenced_ring = NULL;
obj->active = 0;
+ obj->pending_gpu_write = false;
drm_gem_object_unreference(&obj->base);
WARN_ON(i915_verify_lists(dev));
@@ -2810,9 +2811,11 @@
return -EINVAL;
i915_gem_object_flush_gpu_write_domain(obj);
- ret = i915_gem_object_wait_rendering(obj, true);
- if (ret)
- return ret;
+ if (obj->pending_gpu_write || write) {
+ ret = i915_gem_object_wait_rendering(obj, true);
+ if (ret)
+ return ret;
+ }
i915_gem_object_flush_cpu_write_domain(obj);
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index f57536a..af01a58 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -775,6 +775,7 @@
i915_gem_object_move_to_active(obj, ring);
if (obj->base.write_domain) {
obj->dirty = 1;
+ obj->pending_gpu_write = true;
list_move_tail(&obj->gpu_write_list,
&ring->gpu_write_list);
intel_mark_busy(ring->dev, obj);